title: Effect of ampicillin on bleeding time in very low birth-weight neonates during the first week after birth.
abstract: OBJECTIVE
  On the day of birth, the bleeding time of very low birth-weight (VLBW, <1500 g) neonates is generally prolonged, compared with term neonates. However, their bleeding time generally improves (shortens) over the next 7 to 10 days. Ampicillin can prolong the bleeding times of term and late preterm neonates, but its effect on VLBW neonates, who already have a somewhat prolonged bleeding time initially, is not known.
  
  
  METHODS
  This was a prospective, single-centered, paired, before vs after test of the effect of ampicillin on template bleeding time and PFA-100 time (platelet function analyzer). Ampicillin was dosed at every 12 h intravenously, but decisions about discontinuation were made by the responsible clinician, independent of this study.
  
  
  RESULTS
  A total of 20 VLBW neonates were studied. They ranged from 23- to 30-weeks gestation at birth and weighed 500 t 1410 g. Initial bleeding times averaged 166 s (95% CI, 138 to 194) and initial PFA-100 times averaged 119 s (95% CI, 90 to 148). In all, 10 had ampicillin dosing stopped after a shorter course (4 to 7 doses) and 10 had it continued for a longer course (10 to 15 doses). Blood cultures were sterile in all 20, and no differences in laboratory or clinical features were found between those treated with a shorter vs longer course. After stopping the ampicillin following a short course the bleeding times and PFA-100 times were similar to the initial values. However, after a longer course the bleeding times were prolonged by an average of 2 min, to 284 s (95% CI, 242 to 326; P=0.001 vs initial). The PFA-100 times also trended longer by an average of 44 s (P=0.07). The number of doses of ampicillin received in the first week correlated with the degree of prolongation in bleeding time (r=0.68).
  
  
  CONCLUSIONS
  Over the first week of life, a period when the bleeding time of VLBW neonates normally shortens, the opposite occurred (the bleeding time lengthened) if ≥ 10 doses of ampicillin were administered.
authors.affiliation: Intermountain Healthcare, McKay-Dee Hospital Center, Ogden, UT 84403, USA. mark.sheffield@imail.org
authors.forename: M J
authors.initials: MJ
authors.lastname: Sheffield
authors.forename: D K
authors.initials: DK
authors.lastname: Lambert
authors.forename: V L
authors.initials: VL
authors.lastname: Baer
authors.forename: E
authors.initials: E
authors.lastname: Henry
authors.forename: A
authors.initials: A
authors.lastname: Butler
authors.forename: G L
authors.initials: GL
authors.lastname: Snow
authors.forename: R D
authors.initials: RD
authors.lastname: Christensen
mesh_terms: D000667:Ampicillin / Q000008:administration & dosage* / Q000009:adverse effects; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000009:adverse effects; D001760:Bleeding Time; D001792:Blood Platelets / Q000187:drug effects*; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D019102:Infant, Very Low Birth Weight; D007363:Intensive Care Units, Neonatal; D008297:Male; D011446:Prospective Studies; D012016:Reference Values; D018570:Risk Assessment; D047929:Term Birth; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D000667:Ampicillin